Area VI: Pollution

VIB1: Hazards to Human Health

19-1 Risk, Probability, and Hazards

Risks and hazards—some avoidable, some not—compromise everyday life risk: measure of your likelihood of suffering

harm from a hazard such a hazard may cause injury, disease,

economic loss, or environmental damage risk assessment: probability, mathematical

statement of likelihood that harm will result risk management: deciding whether or how to

reduce a risk to a certain level and at what cost

19-1 Risk, Probability, and Hazards four major types of hazards

cultural hazards include unsafe working conditions, smoking, poor diet, drugs, unsafe sex, poverty, criminal assault, etc.

chemical hazards are harmful chemicals in the air, water, soil, and food.

physical hazards include radioactivity, fire, earthquake, floods, etc.

biological hazards come from pathogens, pollen, other allergens, and animals such as bees and poisonous snakes

19-3 Chemical Hazards toxic chemicals can kill, and hazardous

chemicals can cause various types of harm a toxic chemical can cause temporary or

permanent harm or death to humans or animals

a hazardous chemical can harm because it is flammable or explosive or because it irritates or damages skin or lungs or induces allergic reactions

19-3 Chemical Hazards toxic and hazardous chemicals, cont.

three major types of potentially toxic agents mutagens are chemicals or ionizing

radiation that mutate DNA molecules; no safe threshold (?)

teratogens are chemicals that cause harm or birth defects to a fetus or embryo; alcohol and thalidomide are examples

carcinogens are chemicals or ionizing radiation that cause or promote cancer

19-3 Chemical Hazards some chemicals disrupt the immune,

nervous, and endocrine systems the immune system protects the body against

disease and harmful substances neurotoxins are types of poisons that attack

the nervous system that consists of the brain, spinal cord, and peripheral nerves

the endocrine system releases small amounts of hormones that turn on and off bodily systems controlling reproduction, growth, development, learning ability, and behavior

20-6 Effects of Pollution protection from air pollution – respiratory

system hairs in the nose filter out large particles sticky mucus lines the respiratory tract to

capture smaller particles and some dissolved gases

sneezing and coughing expel contaminated air and mucus

prolonged or acute exposure to air pollutants can overload natural defenses

20-6 Effects of Pollution respiratory system, cont.

several respiratory diseases can develop such as asthma, lung cancer, chronic bronchitis, and emphysema

people with respiratory diseases, older adults, infants, pregnant women, and people with heart disease are especially vulnerable to air pollution

20-6 Effects of Pollution air pollution kills about 3 million

people/year, mostly from indoor air pollution in developing countries

deaths in U.S. range from 150-350 k people/yr a large diesel-powered bulldozer produces as

much air pollution as 26 cars the EPA proposed emission standards for

diesel-powered vehicles that go into effect in 2007 with full compliance by 2012; expected to reduce diesel-fuel emissions by 90%

19-3 Chemical Hazards some studies indicate that human-made

chemicals can act as hormone or endocrine disrupters

called hormonally active agents (HAAs) may disrupt human immune functions and may

have adverse reproductive and developmental effects on vertebrates exposed to them

we do not know if they pose a threat to human health, even at low levels in the environment

Fig. 19-7 Hormones

19-3 Chemical Hazards existing laws consider chemicals benign

unless the opposite is proved (not always true); estimating toxicity is difficult, uncertain, and expensive

the toxicity of most chemicals has not been determined

only 2% of the chemicals in commercial use have been adequately tested to determine whether they are carcinogens, teratogens, or mutagens (source ?)

19-3 Chemical Hazards existing law, cont.

99.5% of commercially used chemicals in the U. S. are not regulated

most chemicals are considered innocent until shown to be guilty.

there are also not enough funds, personnel, facilities, and test animals available to provide information for all the chemicals we encounter in our daily lives

19-3 Chemical Hazards precautionary principle says that if there is

plausible evidence that a chemical/technology may cause significant harm, we should act to prevent/reduce its risk

two major changes in evaluating risks: assume new chemicals and technologies

harmful until studies show otherwise remove from market existing chemicals and

technologies that appear to have a strong chance of causing harm until their safety is established

19-3 Chemical Hazards precautionary principle, cont.

the EU agreed to a global treaty that would ban or phase out use of 12 of the most notorious persistent organic pollutants; treaty went into effect in 2004

there is controversy about whether this precautionary principle will stifle or promote research and new technology

19-4 Biological Hazards diseases

non-transmissible tend to develop slowly have multiple causes not caused by living organisms do not spread from one person to another examples: are cancer, diabetes, asthma,

malnutrition, and blood vessel disorders

19-4 Biological Hazards diseases, cont.

transmissible caused by a living organism can spread from one person to another spread in air, water, food, and body fluids

and by some insects and vectors the World Health Organization stated that:

30% of all deaths per year are caused by non-transmissible cardiovascular disease

26% by transmissible infectious disease 12% by non-transmissible cancers

Fig. 19-8 Pathogens

T-even virus

19-4 Biological Hazards bacteria can reproduce rapidly and can

become genetically resistant to widely used antibiotics through natural selection

bacteria can transfer this resistance to nonresistant bacteria

human travel and trade spread bacteria rapidly across the globe

doctors overuse antibiotics the availability of antibiotics in many countries

without a prescription makes them abundant

Fig. 19-9a Dengue fever

Fig. 19-9b Malaria

Fig. 19-9c Yellow fever

19-4 Biological Hazards bacteria resistance, cont.

antibiotics have been used in livestock and dairy animals to control disease and promote growth; public pressure has caused some phasing out of antibiotic use in cattle

overuse of pesticides increases pesticide resistant insects and other carriers of bacterial diseases

we should focus on learning how to weaken effects of infectious microbes by making them less virulent rather than wiping them out

19-4 Biological Hazards tuberculosis kills about 1.7 million

people/year and infects about 9 million annually

global epidemic, and many people do not know that they have been infected

several factors account for the recent increase in TB:

lack of screening, especially in developing countries

increased population growth, urbanization means greater contact between people

Fig. 19-12 Tuberculosis

Tuberculosis

19-4 Biological Hazards tuberculosis, cont.

factors, cont. there are genetically resistant strains of TB

to almost all effective antibiotics the spread of AIDS weakens the immune

system and allows the TB bacteria to multiply

there must be early detection and treatment of people with active TB to slow the spread of the disease

19-4 Biological Hazards viral disease is a great threat to people

worldwide biggest killer is HIV, transmitted in a variety of

ways; infects at least 5 million people/yr; about 3 million people/yr die with AIDS; leaves body defenseless

influenza virus is the second biggest killer from viral infection; kills about 1 million people/yr

hepatitis B virus (HBV) damages liver, kills ~1 million people/yr; transmitted like HIV

Fig. 19-11 Deadly infections

Fig. 19-10 Viral reproduction

19-4 Biological Hazards viral disease, cont.

health officials are concerned about the emergence of Ebola, West Nile virus, and severe acute respiratory syndrome (SARS) in recent years

vaccines are the best weapons against viruses; they stimulate the body’s immune system to produce antibodies to ward off viral infections

19-4 Biological Hazards a still rapidly growing health threat is the

spread of AIDS about 33 million people worldwide live with

HIV/AIDS each day about 14,000 more people are

infected with HIV within 7–10 years at least half of those with

HIV develop AIDS, with most of them in the 15–24 age group and most in developing countries, especially in sub-Saharan Africa

People with HIV/AIDS

Fig. 19-13 AIDS age structure

19-4 Biological Hazards AIDS, cont.

there is no vaccine for HIV, no cure for AIDS life expectancy in sub-Saharan Africa has

dropped from 62 years to 47 years the death toll to AIDS could reach 5 million a

year by 2020 the WHO stated that five major strategies are

needed to slow the spread of AIDS reducing the number of new infections

below the number of deaths

19-4 Biological Hazards AIDS, cont.

strategies, cont. concentrate on the groups that are most

likely to spread the disease such as truck drivers, prostitutes, and soldiers

provide free HIV testing use mass advertising and education for

adults and school children provide free or low-cost drugs to slow the

progress of the disease (?)

19-4 Biological Hazards malaria kills about 1 million people a year

and is caused by a parasite that is spread by the bites of certain mosquitoes

caused by 4 species of protozoan parasites in the genus Plasmodium

the parasite circulates from mosquito to human and back to mosquito

the cycle repeats until immunity develops or treatment is given or the victim dies

19-4 Biological Hazards malaria, cont.

malaria was curtailed in 1950s and 1960s by spraying and draining swamps and marshes, but most species of mosquito have become genetically resistant to insecticides and anti-malarial drugs

in 2002, scientists announced that they had sequenced the DNA of mosquito, Plasmodium

Plasmodium

Fig. 19-14 Malaria life cycle

Malaria risk

19-4 Biological Hazards malaria, cont.

currently, prevention is the best method to control its spread; methods include:

fixing leaking water pipes using mosquito netting cultivating fish that feed on mosquito larvae planting trees that soak up water in marshy

areas using zinc and vitamin A supplements to

boost resistance in children

19-4 Biological Hazards we can sharply reduce incidence of

infectious diseases if the world is willing to provide the necessary funds and assistance (or if people change their behavior)

death rates from infectious diseases in developing countries are high

about 10% of global medical research and development money is spent on infectious diseases in developing countries (is that a lot or a little?)

19-4 Biological Hazards incidence of infectious diseases, cont.

research on antibiotics and vaccines has decreased because they are difficult and costly to develop and produce lower profits compared to medicines used for chronic diseases (government’s fault?)

about 1/3 of the world’s people lack access to clean drinking water and sanitation facilities

children under five make up about 10% of the world’s population, but account for 40% of global illness

19-4 Biological Hazards incidence of infectious diseases, cont.

global death rate dropped by about 2/3 between 1970 and 2000; number of children immunized between 1971 and 2000 went from 10% to 84% and saved an estimated 10 million lives a year

19-4 Biological Hazards bioterrorism involves releasing infectious

organisms into air, water, or food supplies biological warfare agents are easy and cheap

to produce in a small area recombinant DNA techniques are used to

produce more virulent, faster acting organisms, and they are resistant to antibiotics

many people now have the knowledge to make recombinant organisms, and some of these people live in poverty (really?)

Fig. 19-16 Harmful biological agents

19-4 Biological Hazards bioterrorism, cont.

biological weapons can be carried in small vials that are difficult to detect

scientists are experimenting with insects (such as bees, beetles, moths, and crickets) to see whether they can be used as environmental monitors of chemical and biological agents

DNA detectors are also being developed to test for biological agents

19-5 Risk Analysis there are scientific ways to evaluate and

compare risk, to decide how much risk is acceptable, and find affordable ways to reduce risk

risk assessment involves identifying hazards and evaluating their associated risks

avoidance of cultural hazards also longevity of life

Fig. 19-17 Comparative risk analysis

19-5 Risk Analysis estimation of risk for complex technology is

difficult due to unpredictability of human behavior, human error, and sabotage

system reliability (%) = technology reliability x human reliability

one way to make a system more foolproof or failsafe is to move more of the potentially fallible elements from the human side to the technical side

chance events can still cause problems

Fig. 19-18 Deaths per year

19-5 Risk Analysis results of risk analysis are usually uncertain

key questions involved in evaluating the reliability of risk analysis:

How reliable are risk assessment data and models?

Who profits and who suffers from letting harmful chemicals into the environment?

Should estimates apply to short-term or long-term risks; who should decide this?

Who should do a specific risk analysis, and who should review the results?

Fig. 19-19 Risks

19-5 Risk Analysis results of risk analysis, cont.

key questions, cont. Should the primary goal be to determine

acceptable risk or to figure out a way to do the least damage?

Should cumulative effects be considered, or should risks be considered separately?

How widespread is each risk? Should risk levels be higher for workers

than for the general public?

19-5 Risk Analysis results of risk analysis, cont.

key questions, cont. What is the acceptable level of risk and to

whom? there are advantages of risk analysis such as

organizing and analyzing available scientific information and the identification of significant hazards

results are often very uncertain; regulators usually divide the best results by 100 to 1,000 to provide the public a margin of safety

19-5 Risk Analysis risk management means answering the

following questions: How reliable is the risk analysis for each risk? Which risks have the highest priority? How much risk is acceptable? How much is a life worth? How much will it cost to reduce each risk to an

acceptable level? How should funds be spent to provide the

greatest benefit?

19-5 Risk Analysis risk management questions, cont.

How will the risk management plan be monitored, enforced, and communicated to the public?

most people are poor at evaluating their relative risks because information is misleading and people have irrational fears

example: driving a car vs. _______

19-5 Risk Analysis What factors distort our sense of risk, and

how can we become better at evaluating risk?

one factor is the degree of control we have another factor is fear of the unknown if the risk is voluntary rather than forced, we

will have a different view of the risk itself the catastrophic or chronic nature of the risk

will also influence our perception of it perception of unfair distribution

19-5 Risk Analysis to become better at risk analysis, one must

analyze, compare, and focus on risks from one’s individual lifestyle

carefully evaluate what the media presents; it is often an exaggerated view of risks

compare risks and evaluate the risk of an action compared to other risks

concentrate on the most serious risks to life and health, and do not worry about the small risks and those over which you have little or no control